Portable bow saw



May 18, 1954 A. w. MALL EIAL PORTABLE BOW SAW Filed July 22, 1950 m M y. l

ART/1'01? W MALL.

IVOBLE SIIGRWOOD AR/VO Hesse 11/. W, M

Patented May 18, 1954 PORTABLE BOW SAW Arthur W. Mall, Flossmoo and Noble Sherwood, Mall Tool Company, Chicago, 111., a corporation of Illinois r, Arno Hesse, Chicago,

Crete, Ill., assignors to Application July 22, 1950, Serial No. 175,394

2 Claims.

The present invention relates to improvements in a power driven bow saw. More particularly it has to do with improvements in apparatus for mounting a cutting chain on a bow saw.

Bow saws have been marketed heretofore that employ a power driven saw chain for cutting. These chains are disposed in rigid mountings that can be adjusted to vary the tension of the chain. Such bow saws enjoy only a limited amount of success due to the fact that the mounting will not yield when the saw chain contacts a knot or a nail in the material being cut or when the movement of the chain is jerky due to pulsating operation of the driving engine and uneven engagement of the sprocket and the chain. This type of rigid mounting therefore results in overstressed links and reduced chain life.

. It is, therefore, an important object of the present invention to provide amounting for the chain of a bow saw that is capable of yieldingly resisting shock loads on the chain.

Another object is to provide a resilient mounting for a chain saw which is arranged to absorb and dampen out shock loads.

.According to the teaching of the present invention a saw chain is mounted on the bow saw and is disposed, at one lower corner, over a driving sprocket and, at the other lower corner, over two spaced idler pulleys. One idler pulley is journalled for rotation on a fixed shaft while the second pulley is rotatably mounted at the free end of an arm that is pivotally mounted on the fixed shaft. Since the chain is disposed over the second pulley, swinging movement of the arm and the second pulley will cause variation in the tension of the chain. This swinging movement of the arm is controlled by an adjustable rod that is pivotally connected to the free end of the rod and is spring urged in a direction tending to tension the chain. Thus the spring will hold the chain in tensioned position but will yield when shock loads are encountered.

Other and further features, objects and advantages of the present invention will become evident to one skilled in the art from the following detailed description taken in connection with the accompanying drawings.

On the drawings:

Figure 1 is a side elevational view of a bow saw constructed in accordance with the teaching of the present invention.

Figure 2 is a sectional view taken on line 2-2 of Figure 1.

Figure 3 is a sectional view taken on line 3-3 of Figure 1.

- Figure 4 is a fragmentary enlarged side elevational view of a portion of Figure 1.

Figure 5 is a fragmentary sectional view taken on line 55 of Figure 4.

Figure 6 is a fragmentary sectional view taken on line 6-6 of Figure 4.

As shown on the drawings:

In Figure 1 the reference numeral It indicates generally a bow saw arranged to be driven by a prime mover (not shown) through a clutch or coupling I 2. A driven sprocket I4 is keyed to a shaft I5 that is in driven engagement, through a suitable gear mechanism (not shown), with the drive members of the coupling I2. Any suitable coupling and gear mechanism may be used. A preferred arrangement is illustrated in the copending application of Arthur W. Mall and Arno Hesse, U. S. Serial Number 76,143 filed February 12, 1949, now abandoned.

The bow saw I0 comprises a drive housing I1, an idler housing I8 and a tubular bow member I9 which telescopes, at each end, inside the housings. Sleeve clamps 20 and 2|, integrally formed on the drive housing I 1 and the idler housing I8 respectively, clamp the ends of the bow member I9 to the housings.

The drive housing I1 includes a central hub 23 in whichthe shaft I5 is journalled and a flat wall member 24 to which one end of a chain guide bar 26 is secured by a bolt 21.

The idler housing I8 has spaced wall members 29 and 30 connected by a transverse wall 40. Figure 4. The other end of the guide bar 26 is secured by a bolt 32 to the wall 29 while a handle 33 is integrally formed on the transverse wall 40. As best seen in Figure 5, a shaft 35 is secured infixed position in openings 36 and 31 of the opposed walls 29 and 36 respectively. A spring clip 39, at each end of the shaft, prevents axial movement thereof.

A composite lever AI is pivotally mounted at one end on the shaft 35 and carries, at its free end, a pin 43 which is secured between side plates 44 and 45 of the lever 41. Reinforcing ribs 46 extend between the side plates 44 and 45 to hold them in spaced relation while idler pulleys 4'! and 48 are rotatably journalled on the shaft 35 and the pin 43 respectively between the side plates. Spacer washers 56 are disposed on each side of the pulleys 41 and 46.

Referring to Figure 1, it will be seen that an arcuate guide track 52 is disposed inside the tubular bow member I9. The track 52 has upstanding spaced side walls 53 and 54, Figure 2,

and a bottom wall 55 connecting the side walls.

For the purpose of locking the guide track in the bow, the track is provided with a hooked end 51,

Figure 1, that extends through an opening 58 in the tube for engagement with the wall of the tube. The other end of the guide track 52 has an ofiset tab 16 it that extends througmanmpening; Si in the tubular member. The guide trackanaycbe made of a resilient material such as steel and formed with a lesser degree of curvature or bows--1 ing than the tubular member. Then, whenitlisl. positioned in the tubular member, it isb'ent w the shape shown in Figure :1 .andris firmlyaheld in place by virtue of its normalrtendencyrto.req turn to its unstressed condition'.':

A saw chain 63, shown in Figure 1 as a dotted line to avoid confusion, is disposedtover-ethedrive sprocket M, in the guide track 52, around'the idler pulleys iii and 48, and the guide :traclof the guide bar 28. It will be recognized, of course, 20 that,:since--the guide pulley 48 -is :mounted onzthe free end of the --swingable1-composite :JGTYBX'dl-L; swinging movement ofthedever: dl-labout-lthe shaft is efiective to vary wtheetensionrofiithe, chain,

Adjustment of the tension offithe chainlfiit accomplished by means of a yoke 65, F lg'urelfi,- which. straddles theside plates and";'ofthe l'veir'fl l and is 'pivotallymounted on the 'pin13. The yoke has a threaded .shank "61 "which 0 passes 'fi'eely through an opening; 68 ,1 Figure "4," in'thewall 18 and through a coilspringjilliior threaded," adjustable engagement in a nut "Ill: Aispring clip IE/secured to a projecting arm-'13? of'the housing l 8; has a projecting "end "which 35 engagesa slot in" the nut 10 to prevent rotation of "the nut when the desired adjustmentis'r ob tainedfi Itwill' be evident that the coil spring-fiflkactii'ig between the wall it and the'nut *lflfresiliently tensions the chain andprovidesa yielding mounting for -the chain.

From the foregoing description it: will-be seen that there is provided in this invention a simpl efficient manner of mounting azclfainorr a -bow-" saw; This mouting features -a tensionirigmech anism that is accessible to the operator for quick": adjusting; Further-,1 tlre'atensioningndevloe sprovids Fa resilient rmounting that wvillatemporarilyi yield when'iah'e chain contacts anrobstrnctiomrint 50 the wood thus preventing'damage-to the'chainzandii theeb ow i saw;-

It will beunderstoodathat .modificationssandff variations may beefiected WithOHHdBPQTtiDgiROm'l theescope of the novel concepts Off the epresentw. 5 5

invention;

We .claim:as FOLlI" invention;

1; In azportable bowsaw having ;a tubular;bow-:r member; a drive shousingffastened'torone sendsbfia saidibow'member, an 'idlerl-housinggfastenedctoe the other end of said bow membe ,l a-sguideebaat; extendinglbetween said drive housinggandqsaid idler housing, and a saw chain riding in said guide bar and through said bow member and trained about a driving sprocket journaled in said driving housing and an idler pulley journaled in said idler housing; a saw chain tensioning device comprising a lever mounted at one end on the shaft of saidfiidler pulley for .pivotarmoyementr within the, idler housing; a second *pu-lley 'rotatably mounted on the extended end of said lever; and Iaalever adjustment mechanism including a rod pivotally, connected to the end of said lever carrying said second pulley by means of a yoke straddling-.Jhe.'secondpulley pinned to the lever, said-:rodiextendingcthrough the wall of said idler pulle'y h'ousing, an adjustable nut carried by said rod, anda spririgmounted in fixed relation to the .idler -housi-ng.,and bearing against the nut to resiliently tension said rod and thereby urge the-second pulley against the saw chain to tension said saw chain in its travel about the idler pulley, thtladl'lVB SIJIOCkBfmfihQ'l guides-bar andzthrnugh thetubnlar bQW-Lu.

2. Inzal-portable bowrsawmavingtaitubularzbowr member, ,a'-. drive housing; fastened-ate *onecend: of: said-bow member; an: idler: :housing :fastened to vthesother end!of :said-:bow member,: aeguidete banwextending 1 between saiddrive housing-zand'f said idler housing, and a 'sawzchain ridingiinmaidz guide :bar :and through rsaidlPboW'memher ands trained-{about a driving rsprocketc-journaledcinz saiddrivin ghousing ;and ,anridlen pulleyjournalecl: in-said .cidlen. housing ;a ssawrchaintztensioningr devicewcomprising a: 'lever :mounted mtcone. send: on: the shaft of said ddler pulley forpivotahinove's merit withinthex-idlen housing; a'rsecondcapulleys rotatably mounted-onr-the :extcnded endcofizsaicl: lever; and a lever adjustmentimechanism include ing:;a=rod;p,ivotally' connected tortheiend of: said levera-icarryings said second zpulley ibyimeanslofsaz yoke.-astraddling-;;the:secondjpulley pinned.to'rtlxe. lever, said rod.fixtendiilggzthroughfather: wa'llzlof: said-.-idler-.-pulleyhousing;rmeansscarriedrby the housing t foi resiliently urging ;the :second pulleys against the saw chain-to :tensiomsaidcsavwuchain: in-=itsr1-tnavel 3 about theiidle'r :pulley;r.tlie:-:dr-ive Sprocket; the: guide" barsandithroughz'theetubularl Bfncncestfiiteddn the.=fi1e oflithis spa/tents,

UNITED STATES PATENTS Number Name; Date.

170,8,1'4i Carey, Dec .7,'.1875-. 9735426 Harley, Oct..18,.1910.l

1,195,945 Mitchell et al.' .Aug,.22,1916; 1,562,732 Arsneau Nov,'.2l,'. 1925; 1,819,145 Erickson Sept;.27,1932; 211091702" Lange Mar, 1,.19385 FOREIGN PATENTS Numbers Country? 78,568 Switzerland .Aug.-;. 1, 1916s 

